I don't think Hunnam was bad in this, per se, but I did find myself incredibly ambivalent about him.
In a more austere or aesthetically driven film that could have worked fine, but much of this had a pretty conventional drama feel to the scenes, even if the overarching story was a bit more elliptical and non-compromising. So I felt like a lot of what I was watching I was supposed to be emotionally moved by, and simply wasn't.
That said, the final scene with his boy was handled well. It was one of about five moments in the 2 1/2 hour flick that I connected with Hunnam's performance.
Technical merits on this were quite good and it's worth watching for Khondji's cinematography if nothing else. And yeah, I liked all the performances around Hunnam, particularly Pattinson's in a rather thankless but sizable part and Sienna Miller was great, glad that she got the final shot, which was a nifty one.
It's funny because in almost every way possible, Mrs. Fawcett is the most interesting character in this story, but her story isn't as interesting as the story of the much less interesting characters. Not sure how that works, but I can see why more of the movie wasn't about her at the same time that I suspect a movie about her would have been a good bit more dramatically compelling.